Changes in climate
dramatically alter the planets snow- and ice-covered cryosphere.
With variations in the earths temperature, thousands of
square miles of snow and ice can accumulate or melt. Changes
in snow and ice cover, in turn, affect air temperature, sea
level, ocean currents, and storm patterns.

Snow and ice help keep the earth cool by reflecting between
60% and 90% of the solar energy that shines on them back into
space. Reduction of snow cover and sea ice may lead to increased
warming, as more solar energy is absorbed.

Climate models suggest that global warming will be felt most
acutely in the polar regions, particularly the Arctic. Researchers
have already observed many changes in the Arctic, including
the warmest temperatures in the last 400 years, an earlier melting
of ice on lakes and rivers, and a decline in the extent of spring
and summer sea ice.

Studying the cryosphere also gives scientists valuable insights
into how and why the earths climate has changed in the
past, how it is currently changing, and what may lie ahead.
Ice at the poles and in glaciers contains detailed records of
past climate, including bubbles that capture samples of the
earths ancient atmosphere. By examining ice corescylinders
of ice taken from deep below the surfacescientists gather
data dating back hundreds of thousands of years.